I have compiled this FAQ from posts on this forum, trade, and other sources.

Sausage skins are usually called casings. Let's look at the options for what to buy to make a 'fresh' sausage.

Our first choice is to whether to use natural casings, made from animal intestines, or to use artificial casings made from beef collagen. Most home sausage makers will choose natural ones, as the consensus is that these make a better quality product. Collagen casings can be used straight from the packaging with no further preparation and so require no further explanation here.

Choosing a casing:

When choosing natural casings, we have 3 main choices:

Sheep - the smallest and the most tender - normal sizes are between 16mm - 26+mm.

Pig (Usually called Hog) - sized between 28mm - 42+mm.

Beef (Sometimes called Ox) - available in 3 main sizes - from around 36-38mm right up to sizes wide enough for large haggis - they are edible, but are usually peeled from the product before use.

It can be seen that the main choice for fresh sausage is between sheep and hog. A sheep casing is used for the thin sausages seen in butchers' shops, and a hog casing for the thick ones.

Hog casings are often recommended for people new to sausage making, as they are less delicate than sheep casings. This is true, but the difference is not so marked that it should put you off buying the casing for the size of sausage you prefer. Casings for products using the larger beef (ox) casings is covered elsewhere.

The majority of casings supplied to the home sausage maker will have been dry salted during preparation. They will be sent to you in a bag containing the casings and dry/damp salt.

Having chosen the type of casing, we now have a choice of 'presentation':

Natural - the casing is in a plastic bag/tub in salt

On rods or tubes - sometimes referred to as 'shirred' - the salted casing is on a hard plastic rod or soft plastic tube

Casings on tubes or rods are marginally more expensive, but are much easier to use: you can slide them directly from the rod/tube onto your stuffing horn/tube .

When you receive your sheep or hog casings in the post they may smell a little; this is normal. The smell should go away when they are stored at fridge temperatures.

When you buy casings, you may come across the term 'hank' used as a measurement. Traditionally, this is 100 yards (approx. 91 metres) of casing; it will be made up of a number of pieces of casing - maybe 15 - 20 per hank.

The casings will require rinsing and soaking in water before being used. The amount of time to soak them varies depending on how tough, old, or dry they are. Whilst suggestions of soaking periods between ½ hour and 2 hours may be commonplace, most authorities favour soaking hog casings for longer, usually overnight, to ensure tenderness.

To prepare casings:

Firstly, decide how much casing you'll need. If your casings are not on rods/tubes, you'll then need to separate this amount from the rest. Often you'll find that the ends of all the pieces are tied together: that's a good place to start. Tease a section of casing away from the rest; don't pull and tug at it, you'll only 'knot it up'. A gentle shake of the mass whilst covering everywhere in salt, often helps. The first time you do this, you'd be best to send the kids to their grandparents/friends/relatives: anywhere really! The language is likely to be 'blue'!

Having extracted the casing you want, rinse it in cold water to remove the loose salt. Then place it in cool water to soak. For those of you that like certainties, use water at 21°C (70°F). For tenderness, soak hog or beef casings overnight in the fridge, and sheep casings for a minimum of 2 hours (I soak sheep casings overnight in the fridge as well, but 2 hours at 21°C should be plenty).

Just prior to stuffing - maybe 15 minutes or so - the casings can be placed in water that's slightly warmer, about 32°C (90°F). It's not essential, but helps lubrication slightly.

I like to flush some water down them when I first put the casing in water and again just before putting it on the stuffing horn/tube. Most people do it once, just before using it.

Opening the end of the casing may seem to be impossible the first time you do it - persevere - it's easier with practice. If you have taps that have a narrow end, you may be able to run water directly into the casing to 'flush' it. This is difficult with most mixer taps. In this case, in the bowl that you're soaking the casing in, open the end of the casing and allow as much of it as you can to fill with water, maybe 200 - 250mm (8-10 inches) or so. Holding the end of the casing, let this water run along the casing in stages; it's easier to do than describe! You can do it just before loading the casing, or as you load it as described shortly. If you use rodded casings, still try to get some water between the casing and the rod, it'll make stuffing the sausage easier.

The casing is now ready to use.

Just a bit of advice - wet casings are slippery things; they'll disappear down the drain quicker than you can say 'Soppresata Salami'! You've been warned!

It's so much better, and so much easier to visualise, in this description by traditional butcher and forum member 'Oddwookiee':

Casings: get a gallon pitcher or huge bowl and have your casings absolutely swimming in warm water. More is better, you cannot in any way over-water them at this stage. In fact, give your casing a bath in a gallon, swish them around to get the salt off, dump the water and give them a fresh gallon to soak in while you're doing your meat work. I never pre-flush salt pack casings, it's not necessary at this stage. Just get them soaked and loose. When you go to stuff, get another container (I use a 4 quart / 4 liter tub with 3 qt/L of water in it for a full hank of casings. I know quart and liter are not the same, but close enough for government work) put the casings in and fill it with warm water and add a couple tablespoons of baking soda to the water. The alkali will lubricate the casings, make any knots slip out and make stuffing easier. Pre-flushing happens the moment before stuffing- grab a casing, stick your index and middle into the opening to spread it out and dunk it in and out of the water, scooping the water into the casing, then start sliding the casing onto your horn while holding the casing between a couple fingers of the other hand to keep the water from pooling in the section on the stuffer horn. The section of water filled casing will be opened up and lubricated by the soda water and will slide onto the horn with no effort at all. When you get to the other end of the casing but before the water splooshes onto your table, just drop the end back into the tub of casings, let it expel the water and you're all set.

This way is a little wetter then some other methods so a lipped table is handy, but it is almost completely hassle free. The biggest problem I've ever had is with a knot in the casing when I first start working the hank apart. If you stuff somewhere that a little water on the floor isn't an issue, or have a way to keep a few drips from making a mess, you're golden.

Also, casings do not stink when wet. If your casings stink, do not use them. When flushed they may have a tiny odor, which is normal, but should not be unpleasant. I've read of people recommending adding lemon juice to the water and I strongly recommend against it. If the casings smell bad enough to need a odor mask, you have bigger problems. You want the casing bath to be alkali not acidic. On top of that, acid of any kind denatures proteins; there is absolutely no reason to deliberately weaken the jacket (even slightly) of your sausage, possibly making a weak spot or further weakening an existing thin spot where it can tear and drop your meat on the floor of the smokehouse. If they have an odor you disagree with, get back to the sink and change the water they sit in a couple more times. Nine times out of ten that will solve the problem without adding more possible points of failure to your process.

Don't soak in vinegar, ever. Add a couple tablespoons of baking soda to your soak water to lubricate them and make stuffing easier.

Whilst Oddwookiee's method may be a little bit too messy for the domestic kitchen, the pen picture he paints of what to do, and more importantly, how to do it, is invaluable - many thanks.

Troubleshooting problems:

"I've done as you say, but the casings are still tough."

Casings are a natural product and so vary in quality, but they shouldn't be tough if prepared as instructed. Certainly, complain to the supplier and ask for a replacement. If this is not possible, fresh pineapple juice, papain, lemon juice, or vinegar in the soaking water may help to soften them. This should only be used as a last resort as it will also weaken the casing; in general terms, Oddwookiee's advice above regarding vinegar and other acidic additives should be followed.